Reduced Vertical Separation Minima (RVSM) requirements dictate substantial improvements in air-data systems and aircraft installation and maintenance. RVSM airspace is any airspace or route between 29,000 ft and 41,000 ft inclusive where aircraft are separated vertically by 1,000 ft (300 m). RVSM decreases the minimum vertical separation from 2000 ft and is being implemented world-wide on a region-by-region basis. Conventionally, minimum vertical separation requirements were 2000 ft and pressure altitude monitoring equipment, which directly measured the pressure outside the aircraft, was used to determine the pressure altitude and provided a proper tolerance to comply with the 2000 ft minimum separation requirement.
With the implementation of RVSM, older pressure altitude measuring equipment and installations may not have sufficient accuracy or reliability to meet RSVM requirements.
RVSM altitude monitoring requirements lead to increased cost for upgrading or replacing conventional air-data equipment and aircraft installations and maintenance. Accordingly, there is a need for a pressure altitude monitoring system that meets RSVM requirements without costly aircraft modifications and testing. Further, there is a need for an algorithm that uses geometric altitude, temperature, and relative wind speed measurements to correct errors in pressure altitude measurements. Further, there is a need for a GPS altitude, temperature, and relative wind speed based synthetic pressure computation system which provides a synthetic pressure altitude and meets the RVSM requirements. Further, there is a need for the use of a geometric altitude that is suitably compensated with temperature and wind measurements, to produce a synthetic pressure altitude measurement. There is also a need for a GPS based synthetic pressure computation system that may be used as an independent monitor in a dual RVSM air data system to help determine whether an RVSM air-data system is in error.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.
An example of the invention relates to a method of generating a synthetic pressure altitude. The method includes providing a static air temperature to a data processing device, providing a wind velocity to the data processing device, providing a ground velocity to the data processing device, and providing a geometric altitude to the data processing device. The method also includes performing a numerical integration based on the static air temperature, the wind velocity, the ground velocity, and the geometric altitude. The wind velocity and ground velocity are used to compensate for pressure gradients.
Another example of the invention relates to a method of determining the pressure altitude of an aircraft. The method includes providing a static air temperature from a temperature sensor on the aircraft, to a data processing device. The method also includes providing a geometric altitude from a position determining system on the aircraft, to the data processing device. Further, the method includes providing a wind velocity, from a flight management system or other source, to the data processing device. Further still, the method includes providing a ground velocity, from a flight management system or other source on the aircraft, to the data processing device. Yet further still, the method includes performing a numerical integration based on the static air temperature and the geometric altitude.
Alternative examples and other exemplary embodiments relate to other features and combination of features as may be generally recited in the claims.